Image intensification devices are constructed for a variety of applications. These devices are particularly useful for both industrial and military applications. For example, image intensification devices are used in night vision goggles for enhancing the night vision of aviators and other military personnel performing covert operations. They are also employed in security cameras, photographing astronomical bodies and in medical instruments to help alleviate conditions such as retinitis pigmentosis, more commonly known as night blindness. Image intensification devices are currently manufactured in two types, commonly referred to as Generation II (GEN 2) and Generation III (GEN 3) type image intensifier (I2) tubes.
Image intensifier tubes inherently produce a type of noise known as scintillation noise. Scintillation appears as a random bright flash of very short duration in the output of the I2 tube. In GEN III tubes, the flashes are typically 30 microns in size and persist for 1 to 3 milliseconds. A digital video camera mounted to an I2 tube captures scintillation as one or more bright pixels. The camera exacerbates scintillation noise by extending the duration of each flash from several milliseconds to a full camera frame period. Scintillation noise suppression, therefore, is especially desirable in intensified video.
In an article, titled “Simple real-time noise removal in intensified low-light-level television images” by Boger and Tur, published 10 Jun. 1992 in Applied Optics, Vol. 31, No. 17, at pages 3196-3198, a method is described for removing scintillation noise using an operator to reduce noisy scintillations. The operator uses, as referred to by the authors, a pixelwise interframe temporal minimum operator. Temporal image averaging techniques are described. Some improvements result from the operator, but undesirable blurring of images also result, especially in situations of moving images.
The present invention addresses an improved system and method for scintillation suppression of video images.